In an aircraft, the outer skin is spaced from the walls and ceiling of a passenger cabin (or other compartment). During a flight, moisture from moist air in the space can condense against the skin and freeze during cruise. During descent, this frozen moisture can thaw and drip back down towards the cabin. The moisture can pass through insulation and other layers, including the passenger cabin ceiling and stowage bins, resulting in the moisture dripping into the passenger cabin.
FIG. 3 is a side view of a prior art moisture control apparatus 300. Conventionally, the moisture control apparatus comprises a moisture absorbing layer 306, for example felt (for example, BMS8-242 Aramid felt, sized ¼ in. ×1.0 in.), the lower surface of which is applied to the upper surfaces of aircraft structures, for example those forming the cabin, such as on the upper surfaces of the ceiling 232 and stowage bins 270. In practice, when moisture drips from an upper portion of the fuselage onto the upper surfaces of the cabin, the moisture control apparatus 300 will usually absorb the moisture droplets 244. However, if too much moisture falls in a single area, the moisture control apparatus 300 can become saturated locally and further moisture droplets 244 added to the moisture absorbing layer 306 will leak 302 out a trailing edge of the felt, such as shown in the prior art view of FIG. 6A.
Additionally, on steeply angled surfaces, moisture droplets 244 can be moving rapidly when the droplets 244 contact the moisture absorbing layer 306. This can cause the moisture droplets 244 to jump 304 over the moisture absorbing layer 306 before the droplets 244 have a chance to be absorbed.